- Bacterial Infections 101 Pictures Slideshow
- Take the Tummy Trouble Quiz
- Hepatitis C Slideshow Pictures
- What's the Difference Between Cephalexin and Amoxicillin?
- What Are Cephalexin and Amoxicillin?
- What Are the Side Effects of Cephalexin and Amoxicillin?
- What Is the Dosage for Cephalexin vs. Amoxicillin?
- What Drugs Interact with Cephalexin and Amoxicillin?
- Are Cephalexin and Amoxicillin Safe to Use While Pregnant or Breastfeeding?
What's the Difference Between Cephalexin and Amoxicillin?
- Cephalexin and amoxicillin are antibiotics used for treating a variety of bacterial infections.
- The drugs belong to different classes. Cephalexin is a cephalosporin antibiotic and amoxicillin is a penicillin-type antibiotic.
- Brand names for cephalexin include Keflex and Daxbia. Brand names for amoxicillin include Amoxil, Moxatag, and Larotid.
- Side effects of cephalexin and amoxicillin that are similar include diarrhea, nausea, abdominal pain, vomiting, dizziness, and skin rash.
- Side effects of cephalexin that are different from amoxicillin include headaches, fever, abnormal liver tests, and vaginitis.
- Side effects of amoxicillin that are different from cephalexin include heartburn, insomnia, itching, confusion, easy bruising or bleeding, and allergic reactions.
What Are Cephalexin and Amoxicillin?
Cephalexin belongs to a class of antibiotics called cephalosporins. They are similar to penicillin in action and side effects. They stop or slow the growth of bacterial cells by preventing bacteria from forming the cell wall that surrounds each cell. The cell wall protects bacteria from the external environment and keeps the contents of the cell together, and without a cell wall, bacteria are not able to survive. Bacteria that are susceptible to cephalexin include Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, E. coli and several others. Cephalexin is used for treating genital and urinary tract infections, bone infections, ear infections, skin and skin structure infections, respiratory infections, pharyngitis, mastitis, and bladder infections.
Amoxicillin belongs to a class of antibiotics called penicillins. Other members of this class include ampicillin (Unasyn), piperacillin (Pipracil), ticarcillin (Ticar), and others. These antibiotics all have a similar mechanism of action. They do not directly kill bacteria, but they stop bacteria from multiplying by preventing bacteria from forming the walls that surround them. Amoxicillin is effective against many different bacteria including H. influenzae, N. gonorrhoea, E. coli, Pneumococci, Streptococci, and certain strains of Staphylococci.
What Are the Side Effects of Cephalexin and Amoxicillin?
The most common side effects of cephalexin are:
- abdominal pain,
- skin rash,
- abnormal liver tests, and
Individuals who are allergic to penicillin may also be allergic to cephalexin. Serious but rare reactions include seizures, severe allergic reactions (anaphylaxis), and low platelet or red blood cell count.
Cephalexin, like almost all antibiotics, may cause mild or severe cases of pseudomembranous colitis, a mild to severe inflammation of the colon. Antibiotics, including cephalexin alter the types of bacteria in the colon and permit overgrowth of a bacterium called Clostridium difficile. Studies indicate that toxins produced by Clostridium difficile are a primary cause of pseudomembranous colitis.
Side effects due to amoxicillin include:
- abdominal pain,
- easy bruising,
- rash, and
- allergic reactions.
People who are allergic to the cephalosporin class of antibiotics, which are related to the penicillins, for example, cefaclor (Ceclor), cephalexin (Keflex), and cefprozil (Cefzil), may or may not be allergic to penicillins.
Serious but rare reactions include:
- severe allergic reactions (anaphylaxis), and
- low platelet (thrombocytopenia) or red blood cell count.
Amoxicillin can alter the normal bacteria in the colon and encourage overgrowth of some bacteria such as Clostridium difficile which causes inflammation of the colon (pseudomembranous colitis). Patients who develop signs of pseudomembranous colitis after starting amoxicillin (diarrhea, fever, abdominal pain, and possibly shock) should contact their physician immediately.
What Is the Dosage for Cephalexin vs. Amoxicillin?
The dose of cephalexin for adults is 1 to 4 grams in divided doses. The usual adult dose is 250 mg every 6 hours. Some infections may be treated with 500 mg every 12 hours. Children are treated with 25-100 mg/kg/day in divided doses. The dosing interval may be every 6 or 12 hours depending on the type and seriousness of the infection.
- For most infections in adults the dose of amoxicillin is 250 mg every 8 hours, 500 mg every 8 hours, 500 mg every 12 hours or 875 mg every 12 hours, depending on the type and severity of infection.
- For the treatment of adults with gonorrhea, the dose is 3 g given as one dose.
- For most infections, children older than 3 months but less than 40 kg are treated with 25 or 45 mg/kg/day in divided doses every 12 hours or 20 or 40 mg/kg/day with one-third of the daily dose given every 8 hours depending on the type and severity of the infection.
- Amoxicillin can be taken with or without food.
What Drugs Interact with Cephalexin and Amoxicillin?
Amoxicillin is rarely associated with important drug interactions.
Are Cephalexin and Amoxicillin Safe to Use While Pregnant or Breastfeeding?
- Cephalexin is excreted in breast milk. Cephalexin should be used with caution or stopped when breastfeeding.
- Penicillins are generally considered safe for use by pregnant women who are not allergic to penicillin.
- Small amounts of amoxicillin may be excreted in breast milk and may cause diarrhea or allergic responses in nursing infants. Amoxicillin is generally considered safe to use while breastfeeding. Amoxicillin is used to treat infections in the newborn.
Cephalexin (Keflex, Daxbia) belongs to a class of antibiotics called cephalosporins. They are similar to penicillins -- the class to which amoxicillin (Moxatag) belongs -- in action and side effects. Both are used to treat various bacterial infections.
Multimedia: Slideshows, Images & Quizzes
Cold & Flu Quiz: Influenza vs. Common Cold
Aches? Pain? Fever? This Cold & Flu Quiz tests your knowledge on the difference between coming down with the common cold and...
Strep (Streptococcal) Throat Infection Quiz: Test Your Infectious Disease IQ
Take the Strep (Streptococcal) Throat Infection Quiz to learn about causes, symptoms, treatments, prevention methods, diagnosis,...
Picture of Strep Throat
Strep infection often produces a distinct pattern of white patches in the throat and on the tonsils, as well as red swollen...
Picture of Influenza Virus
The flu is caused by viruses that infect the respiratory tract which are divided into three types, designated A, B, and C. See a...
Sore Throat or Strep Throat? How to Tell the Difference
Explore the types and causes of a sore throat through pictures, including strep throat, and learn how to find relief from that...
Related Disease Conditions
Group A Streptococcal Infections
Second Source article from Government...
Clostridium Difficile Colitis (Antibiotic-Associated Colitis, C. difficile colitis)
Clostridium difficile (C. difficile) is a bacterium, and is one of the most common causes of infection of the colon. C. difficile...
Pneumonia is inflammation of the lungs caused by fungi, bacteria, or viruses. Symptoms and signs include cough, fever, shortness...
Strep Throat (Treatment, Causes, Home Remedies)
Strep throat is a bacterial infection of the throat. Signs and symptoms of strep throat include headache, nausea,...
Group B Strep
Group B strep are bacteria called Streptococcus agalactiae that may sometimes cause infections both in a pregnant woman and her...
Bronchitis (Acute) Symptoms, Causes, Treatment Remedies, and Cures
Bronchitis is inflammation of the airways in the lung. Acute bronchitis is is short in duration (10 to 20 days) in comparison...
Group A streptococcal infections are caused by group A streptococcus, a bacteria that causes a variety of health problems,...
Chronic Bronchitis (Symptoms, Causes, Treatment, Remedies)
Chronic bronchitis is a cough that occurs daily with production of sputum that lasts for at least three months, two years in a...
Is Pneumonia Contagious?
Pneumonia is inflammation of the lung usually caused by bacterial or viral infection (rarely, also by fungi) that causes the air...
Is C. diff (Clostridium difficile) Contagious?
C. diff, or Clostridium difficile, is a bacteria that infects the colon. C. diff bacteria can be found on furniture, bathroom...
Treatment & Diagnosis
- Cold & Flu FAQs
- Strep Streptococcal Throat Infection FAQs
- Pneumonia ... Quick New Urine Test
- Strep Throat Diagnosis & Treatment
- How Long Does It Take Strep to Go Away?
- Does Stress Cause Ulcerative Colitis?
- Does IBS Cause Crohn's Disease or Ulcerative Colitis?
- Can Microscopic Colitis Cause Joint Pain?
- How Long Is Pneumonia Contagious?
- Strep Throat Complications
- Sore Throat: Is It Mono or Strep Throat?
- Strep Throat Symptoms
- Pneumonia Symptoms
- Sore Throat: Virus or Strep?
- Pneumonia Treatment
- Strep Throat Natural Home Remedies
Medications & Supplements
Infectious Disease Resources
Health Solutions From Our Sponsors
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
FDA Prescribing Information